A gate valve is known from DE 43 20 185 A1. There, a valve plate is conducted in a movable manner within a rack frame that can be installed on a wall in front of an outlet opening. A sealing arrangement with two ring seals situated on each side of a sealing ring is provided in the area of a passage in a wall plate of the rack frame. By means of a wedge arrangement with several wedge pieces arranged on the gate valve and the rack frame, the gate valve is pressed, transverse to its movement direction against the sealing arrangement, when the valve plate arrives at a closing position covering the passage.
With such gate valves with a wedge system, the valve plate is moved, during almost its entire stroke, with a clearance within the rack frame. Only at the end of the closing stroke is the wedging of the wedge pieces that are firmly arranged on the valve plate and the rack frame effective, so that the valve plate is pressed against the sealing only just before the complete shutoff. In this way, the friction and the actuating force can be decreased and the wear and tear, reduced. However, the valve plate lifts off relatively fast from the sealing upon opening, so that a leakage also appears quickly on the entire valve plate. Since the wedge pieces affixed on the valve plate and the rack frame must be moved, collision-free, past one another during the stroke movement, a lateral movement of the wedge pieces is also required. Especially with larger gate valve dimensions with several wedge pieces located above one another, therefore, the side sections of the rack frame must have a corresponding width and stability. For this reason, however, the use of material and the size are increased.
Therefore, gate valves are also already known, in which the valve plate, conducted almost free of play in outlining frame profiles, is pressed in a defined manner against the individual sealing profile by means of slide profiles made of plastic as a rule. With such a structure, only the actual gate valve opening is released, whereas the areas on which valve plate and sealing are in contact are tight. Furthermore, the valve plate is conducted free of play during the entire stroke, wherein vibrations can be avoided during operation. However, since the valve plate is pressed during the entire stroke with the sealing, correspondingly higher actuation forces are needed for the movement of the valve plate. As a result of the constant pressing of the valve plate with the sealing, the friction during the actuation is also increased and thus, also the wear and tear of the sealing. If leakage occurs, moreover, the sealing force cannot be increased further.